High pressure permanent molding



Dec. 18,1962 R` E. wlLcoxoN HIGH PRESSURE PERMANENT MOLDIRG Filed Aug.4, 1960 INVENToR. Qa/,oh E #Vf/casco ATTYS` Dlec. 18, 1962 n.:-:.w1|.coxoN 3,068,539

HIGH PRESSURE PERMANENT Momma IN VEN TOR.

,Qa/,olv E14/Wears ATTYS.

Dec. 18, 1962 Filed Aug. 4, 1960 R. E.WILCOXON HIGH PRESSURE PERMANENTMOLDING 4 Sheets-Sheet 5 ATTvs.

II'VVENTOR. PV//caxon Dec. 18, 1962 R. E. wxLcoxoN HIGH PRESSUREPERMANENT MOLDING 4 Sheets-Sheet 4 Filed Aug. 4, 1960 humm INVENToR.Qa/,o E.' M/f/coxon y ATTYS.

ite rates 3,663,539 HIGH PRESS E PERMANENT MOLDING Ralph E. Wiicoxon,Cleveland, hio, assigner to Thompson Ramo Wooldridge Ine., ClevelandGillo, a corporation of Shin Filed Ang. d, 195i?, Ser. No. 46,695 12Claims. (Cl. 22-93) This invention relates to the manufacturing ofpistons and more particularly to improved methods and means for highpressure molding of internal combustion engine pistons from molen metalinvolving iiiling of a die cavity therewith, followed by the insertionof a plunger in the metal to form a core, and controlling of the flow ofmetal under pressure, thereby producing a piston requiring no insideinish.

In accordance with this invention, lightweight metals, such as aluminumand aluminum alloys, may be heated to above their melting points andpoured into a split die mold. A sealing collar is then wedge iitted on acomplementarily tapered rim of the split die mold. The collar and moldrim define therebetween a chamber for receiving the molten metaloverilow from the die cavity lwhich communicates with the die cavitythrough a narrow, restricted passage for restricting metal iow and tohold the pressure in the die cavity.

The plunger type core has a snug sliding fit in the collar and, as thecore is urged into the molten metal pool, the excess metal flows intothe overow chamber.

The molten metal is poured into the die cavity in a quantity in excessof that required for molding of the piston. The stationary base of thedie assembly includes an ejector housing which forms the base of the diecavity. When the molten metal has cooled suiiiciently, the movable coreassembly is retracted, and a pneumatically or hydraulically operatedpiston assembly moves the ejector housing which pivots the split diesand pushes out the newly formed piston casting.

A feature of this invention resides in the provision of a spring-biasedcollar carried by the movable core platen which positively pre-seats onthe rim of the split d-ie means securing the die means before themolding pressures are applied to the collar and die assembly by thecore. A further feature of the present invention resides in passaging ofthe split dies in communication with the die cavity in a location wherethe wrist pin bores are to be formed in the casting being molded and thepositioning of movable members in the die passages which, in a firstretracted position, define sump or reservoirs for molten metal and whichmay be movable to an extended position into the die cavity therebyforcing the metal from the reservoirs into the die cavity -to compensatefor volume loss due to cooling caused shrinkage. It has been my exerience that metal injected from a reservoir to cornpensate for coolingcaused shrinkage in the die cavity produces a weaker grain structure inthe area where the metal is injected, apparently because of thedil-'ference in cooling rates and times of the metal initiallysolidifying in the die cavity and the metal subsequently injected.Additionally the grain crystalline growths of the metals are differentwhich appears to cause a weaker interstitial bond between theaforementioned initial and injected metals. This phenomenon is visibleto the naked eye as is hereinafter more fully explained.

By injecting the metal in the area from which the wrist pin bores are tobe drilled or otherwise removed, I effectively eliminate substantiallyall of the weakly bonded injected metal from the formed piston. Theabove arrangement eliminates the heretofore required gates, riserformation, related molding components and, in addition,

n 3,068,539 EQ@ Patented Dec. 1s, 1962 reduces the metal setting timewithin a fraction of tha heretofore required in the prior art.

It is, therefore, a general object of the present invention to provideimproved pistons.

Another object of the present invention is to provide a method ofmolding pistons under high pressure conditions.

A still further object of the present invention is to provide a methodof making molded aluminum pistons.

A still further object of the present invention is to provide a methodof manufacturing internal combustion engine type pistons by filling thedie cavity of molding apparatus with molten metal followed by theinsertion of a core into the metal in the cavity to form the interior ofthe piston and thereafter controlling the liow of metal under pressure.

It is yet another object of the present invention to provide highpressure molding apparatus for the manufacture of components ofirregular contour.

A still further object of the present invention is to provide apparatusrequiring a minimum number of parts for high pressure molding of moltenmetal.

Yet another object of the-present invention is to provide pistons moldedunder high pressure conditions requiring a minimum of nishing and oftine' grain and high structural strength.

A still further object of the present invention is to provide apparatusfor high pressure molding of pistons'which is simple and compact inconstruction and eicient and high speed in operation.

These and other features, objects and advantages of the presentinvention will become more apparent upon a careful consideration of thefollowing detailed description, when considered in conjunction with theaccompanying drawing illustrating .a preferred embodiment of the presentinvention, wherein like reference characters and numerals refer to likeor corresponding parts throughout the several views. i

On the drawings:

FIGURE l is a front elevational view of molding apparatus according tothis invention.

FIGURE 2 is a fragmentary view in cross-section of the apparatus ofFIGURE 1.

FIGURE 3 is a view taken along lines III-III of FIGURE l.

FIGURE 4 is a fragmentary view in cross-section illustrating the excessmetal plungers in the retracted position.

FIGURE 5 is a fragmentary view in partial cross-section illustrating theexcess metal plungers in extended position. l

FIGURE 6 is a fragmentary plan view of a formed piston illustrating theinjection area of the weakened bond between the initial and compensatingmetal.

FIGURE 7 is a fragmentary view in cross-section of the plunger injectedmetal, and v FIGURE 8 is a view in cross-section of a piston formedy inaccordance with the present invention.

As shown on the drawing: Briefly stated, apparatus for pistonmanufacture illustrated in FIGURE l may include a base support membery11 carrying a die assembly base l2, having secured thereto an ejectorassembly base I3 which has pivotally mounted thereto a pair of ejectoractuator arms 13a and 13b which are adapted to be moved by contact withan ejector housing I4 operatively responsive to a pneumatic or hydraulicpiston assembly 14a. Removably held by a plurality of restrainingmembers 15 is a generally rectangularly shaped split die comprising diemembers 16 and die member 16', each of which is secured to the ejectorYarms 13a and 13b respectively, by llanges 15a and each .of which ispro-vided with `a raised annular ange or rim 16a.

A movable platen 18 seats a plurality of springs i9 in a sleeve .2b.Springs 19 urge a movable collar 21 from Contact with the sleeve 2t? andsurround a movable collar support means 2in. Collar 21 has a peripheralharige complementary' to the rims 16a of the split dies for holding thedies securely together and'for cooperating with the die members todeiine an overflow chamber for receiving molten metal from the diecavity. Movably carried by the platen 1S is a die core assembly 17adimensioned to the desired internat conguration of the piston to beformed.

The platen 18 is movably carried by a shaft 22 which is actuated by apneumatic or hydraulic piston assembly 23 of conventional construction.A stationary platen 24 may support the piston assembly 23 and may serveas a support for a plurality of guide members 25 for the movable platen18 and the core assembly 17a.

Referring particularly to FIGURE 2, wherein the core assembly 17a isshown in the retracted position, each of the ejector follower arms 13aand 13b is provided with a pivot 13e and 13d, respectively, each ofwhich is journaled in a pair of raised bearing members 26 and 27 securedto the ejector assembly base 13, as by bolts 28 and 29 respectively. Theejector y'assembly base 13 is recessed as at 30 and 31 to permit a widerpivot arc for members 13a and 13b (FIGURE 2 and 3) during operation.

Centrally located within the base 13 is a bore, indicated by the numeral32, which is provided with a tapered shoulder 32a and a counterbore 33for receiving the ejector 14 and for providing a shoulder 34 for Vtheperipheral annular flange 3 5 of the ejector 14.

Similarly, each of the T shaped pivotable arms ma and 13b is inwardlytapered from the top surface thereof, as shown in FIGURE 2 to preventbinding vthereof with theejector 14 during the ejection operation.

As more clearly appears in FIGURE 3 the split die members 1 6 and 16 arerectangular in shape and when assembled define a die core receivingcavity. The split die members 16 and 16 are held in position by aplurality of bracket members carried by the actuator arms i3d and 13band ythe die anges 15a secured thereto.

The core guides may, if desired, pass through the hase member 12 and besecured in the base member 11.

As appears in FIGURES 2 and 5, the ejector assembly may b e providedwith means for cooling the split die members thereby reducing the timerequired to solidify the molten metal. For this purpose, the ejector 14may be provided with an inlet conduit 37 for introducing the coolingmedium into an internal passage 38 which communicates with an annularpassage 39 in the upper portion of the ejector which provides the basefor the split die means. The annular passage 39 in the ejector head 14hcommunicates with a similar internal outlet passage and port (not shown)for discharge of the coolant medium from the ejector.

The two die members 16 and 16' define therebetween the molten metal diewell or cavity 48, and which, for purposesof the example hereof, iscylindrical in contiguration.

As aforementioned, the upper core portion as appears in FIGURE lincludes a stationary platen 24 which may carry the core piston assembly23 and may serve as support means for the guides 25 of the core carryingmovable platen 13. Guides 25 may be secured at the lower end in thesupport member l2 and to the stationary platen 24 at the upper ends .inthreaded engagement therewith as by nuts 47 and 48a.

As appears in FIGURE l, the movable platen 18 has secured thereto orformed integral therewith an upper boss 49 which is adapted to securethe piston rod 22 of the core piston assembly 23 to the platen 18.Secured as by bolts Si) to the under side of the movable platen 18 isthe peripherally hanged sleeve 20.

Inwardly of the flange 51, the sleeve or ring 2@ is bored to receive theplurality of movable threaded members 21a adapted to retain and supportthe collar 21. Adjacent the collar 21, the ring Zit is provided with aplurality of annularly spaced bores 52 to receive the springs 19 whichurge the collar from contact with the ring 20. Each of the springs 19seats against the shoulder provided by the complementary counterbore 52ain the ring 2E? and is bottomed against the collar Zi. Each of the pinreceiving bores are also counterbored, as indicated by the numeral'52!7, adjacent the movable platen 18 to permit movement of pins 21a andcontact between the opposed faces S3 and 54 of the ring and collarduring the molding operati-on, as clearly appears in FGURE 5, The heads2lb of the pins 2id prevent unlimited movement of the pins.

The core head 17a is prevented from rotating by a key 59, as appears inFIGURE 7, and is removably secured to the ring 2t) as by bolts (notshown) inserted through slots 69 formed in the ring 20.

Centrally located in the core head 27a is a stepped passage defining acooling medium inlet 62 communicating with a passage of smaller diameter63 which is opened at the botom end to permit circulation of a coolingmedium in the fluid passage 64 which comunicates with the uid outletpassage 65. The passage conduit 63 is supported by a plug 66 whichprevents the uid ow from circulation passage 614 into inlet passage 62.Inlet passage 62 cornmunicates with an inlet 66a which may be adapted toreceive the fluid inlet conduit 67 which passes through a bore 69provided in the ring 2t). Similarly, outlet 65 is adapted 'to receiveconduit 70 which passes through a similar bore 7i in the ring Zit. Thusa circulation system is provided for the core assembly 17a whichcooperates with the circulation system provided in the ejector 14 toreduce the time required to set the molten metal being formed in the diecavity '48.

The collar 21 carried by the bolts 21a is provided with an annularchannel 73 inwardly of the periphery thereof and has complementarilytapered surfaces for engagement with the rims 16a of the split diemembers 16 and i6', thereby locking the die members. Thus, the rim 16aand the groove '73 of the collar 21 cooperate, as appears in FIGURES 4and 5, to define a chamber 75 which receives the overflow of moltenmetal from the die cavity 43 through an annular passage 76 of restrictedheight defined by the internal ange 77 of the collar 21 and the opposedtop surface 7S of the split die members. The peripheral liange 79 of thecollar 21 and the rim 16a of the dies i6 and 16 cooperate to preventextrusion of molten metal across the parting line to the exterior of theapparatus.

The core, of course, is shaped to dene the inside diameter of theparticular component to be molded in the apparatus above described, and,for purposes of illustration, is shown shaped to deiine the interior ofan internal combustion engine piston.

Each of the split die members 16 and 16' has a passage 49 communicatingwith the interior of the die cavity adapted to -receive retractable andextendable plunger members 41 and L32, respectively, generally shapedpreferably to the dimension of the wrist pins. The plunger members d andl452 are reciprocably responsive to conventional piston assemblies 43and 44, respectively, which are mounted on a pair of brackets and i6secured to the pivotable ejector actuator arms 13a and tb as by bolts47a.

In operation, molten metal teta may be poured into the die cavity andthe plunger arms #Si and E retracted to the position shown, therebydefining the sump or reservoir chambers it communicating with the diecavity.

The platen i8 is moved downwardly carrying with it the core 17a forinsertion thereof in the molten metal in the die cavity 4% Thespring-biased collar 21 seats on the rim 16a of the split die membersand holds them securely together while cooperating therewith to definethe overflow chamber communicating with the die cavity through thenarrow annular passage 76 before articleforming pressure is applied bythe core 17a in the die cavity.

A coolant is introduced through conduit 37 of the ejector assembly 14,and a coolant is also introduced into the core 17a through conduit 67for circulation and discharge through conduit 70.

ln the second stage of operation, with the collar 21 urged downwardly bythe springs 19 in engagement with the rim 16a before the plunger core17a is fully positioned in the die cavity, the upper platen 18 continuesin its downward movement against the fo-rces exerted by the springs 19until contact is made between the opposed faces S3 of the ring 2G' and54. of the collar 21, as appears in FlG- URE 4. The pins 21a will havebeen moved to their uppermost position in the -recesses 52a (FIGURE 4)when contact between the collar and ring 2d is made. Similarly, with thecore 17a moving into the pool of molten metal 48a, the displaced metalwill flow into the reservoirs 4t) and through the narrow restrictedpassage 76 into the overiiow chamber 75. As aforesaid, the ejector head14a serves as a base or bottom for the die cavity.

The coolant circulation systems in both the core and ejector reduce themetal setting temperature within a range from about 350 P. to about 450F., if water is the cooling medium.

After the metal has partially set, the plungers 41 and 42 are movedinwardly by activation of the piston assemblies 43 and 44 forcing themolten rnetal from the reservoirs 49 into the die cavity to compensatefor the shrinkage of the molten metal which takes place as the metalsolidies. Movement of the plungers 41 and 42 in compensating for metalloss in the die cavity due to shrinkage does not cause displacement ofthe metal through the narrow, restricted passage 76 leading to theoveriiow chamber since the plungers are not moved until the metal in therestricted passage '76 has frozen or solidified before the plungers 41and l2 are extended.

As an example of the material to be molded, a high silicon contentaluminum alloy (MS 143) preferably formed of the following generalcomposition was heated to a pouring temperature of approximately l220F.:

impurities, such as the following may also be included in the alloy:

Percent iron l Zinc O 5 A preferred specific alloy forming the pistonsin accordance with the practice of this invention include the elementsof the general composition set forth above as well as the impurities.

Heretofore, it was necessary to permit a chill time from 2 to 10 minutesin order to permit setting of the molten metal before the formed pistonwas removed from the die cavity. By my method, the time required forsetting is reduced to from about l0 to about 30 seconds, depending uponthe alloy involved and other physical and metallurgical propertiesdesired, since a colder die is used and since pressure forces areemployed to control flow.

For the example above given, the core 17a was constructed of hightemperature die steel material sold by the Crucible Steel Company underthe trade name NU- DLE-V which is a hot-work, chromium-vanadium steel.The die members 16 and 16' of the above example were constructed of alow alloy sold by the Wheelock-Lovejoy Company under the trade nameHY-TEN-B-3X which is a ferrous alloy of nickel and chromium.

In the third stage of the operation, the plungers 41 and Cil 42 may beextended into the die cavity to form the wrist pin bores, as appears inFIGURE 5.

Next, after an appropriate setting time, preferably within the range offrom about 10 seconds to about'30 seconds, has elapsed, the pistonassembly 23 is actuated to retract the core 17a from the die cavity. Asthe core is being initially withdrawn from the die cavity, the springs19 maintain the collar 21 firmly seated on the die rim 16a therebymaintaining the split dies in the locked position until the bolts orpins 21a contact the bottom of the recesses 52a and carry the collarupwardly from contact with the rim 16a of die members 16 and 16. Thus,the die members are securely locked together before pressure is appliedin the die cavity and remain locked by the collar until pressure isremoved from the `die cavity.

The plunger piston assembly 43 and 44 are then actuated to retract theplungers 41 and 42 from the die mold cavity into the passages in thesplit die members. Circulation of the coolants in the ejector assemblyand the core 17a is terminated and thereafter the ejector pistonassembly 14a actuated to move the piston head 44h upwardly in contactwith the ejector 14. The ejector head 14h will continue its upwardmovement whereby the ejector 14 is unseated and the ejector flange 35engages the ejector actuator arms 13a and 13b and pivots the armsupwardly. The split die members 16 and 16 are therefore opened and themolded formed piston is now ready for removal from the apparatus.

The molded piston 85 is easily removed from the ejector 14.

The flash 85a of the molded piston is quite thin near the innerperiphery thereof and may be easily removed. The end surfaces Sib of thesleeve portion of the piston is substantially uniformly fiat requiring aminimum of finishing in this area. No finishing is required on theinside ofthe piston, and the close tolerance permitted by the moldingmethod described above facilitates external finishing of the piston.Thus sound pistons are obtained in less time, thereby increasingproduction rates, and, because of the reduced chill time required, afiner grain piston is obtained having greater structural strength thanwas heretofore considered obtainable Without additional treatment of thepiston. In addition, grain refiners, such as titanium, boron, etc., arenot required as alloy additives. Moreover, in the molding operation,closer tolerances may be obtained than were heretofore possible with thepermanent die type apparatus which must be coated to prevent attack onthe dies in the high temperature, slow cooling methods.

If desired, conventional toggle arrangements may be employed to maintainthe core in the die cavity. For this purpose, the toggle cleats may bepivotally secured to the upper stationary platen Z4 and to the movableplaten 13.

'As appears in FIGURE 6, the effects of different cooling andsolidifying rates is readily apparent visually. The bores 87 in theformed piston from which the plunger was extracted is surrounded by adiscolored area, the limits of which, for purposes of illustration, areindicated by the numeral 8S and the size of which depends upon suchfactors as plunger pressure and the amount of metal being forced intothe die cavities to compensate for cooling caused shrinkage. The dottedline 89 indicates the outer limits of the area from which the wrist pinbore will be drilled, the size of which depends upon such factors as theultimate use of the pisto-n.

FGURE 8 illustrates in cross-section the piston after the finalfinishing and wrist pin bore milling operation. Thus, it will beappreciated that, by positioning the plungers to force the shrinkagecompensating metal into the die cavity in a location where the wrist pinbores are to be drilled, I provide an improved piston having the samestructural strength and grain refinement throughout.

For the aluminum piston of the above example, the flash is merely brokenolf, the piston then subjected to accesso ai heat treatment-for.atperiod of from about lhours at about 400 F. and theri airl quenched,yAfter this treatment, the piston was lready for the machining andmilling operations.

Itwill, therefore, be appreciated that withithe high pressuremoldingapparatus and methods of the present invention, I provide means for theelimination or" gates and riserformations, reduce the time required toset the molded piston, and obtain a pistonV of higher quality than washeretofore obtained without the necessity of addi'- tional alloyelements or fabricating steps and treatments.

Although minor modifications might be suggested by those skilled in theart, it should be understood that I wish to embody within the scope ofthe patent warranted hereon, all such embodiments as reasonably andproperly come within the scope of my contribution to the art.

I claim as my invention:

l. Apparatus for high pressure permanent molding of articles from moltenmetal comprising: die means defining alcore-receiving die cavity; amovable die core-carrying platen; means normally biasing a separatecollar movably carried by said 'platen from contact therewith, saidbiased collar being vadapted to contact saiddie means and remain incontact therewith when said core is being inserted cr retracted fromsaid cavity for' applying molding presssure on molten metal in Vsaidcavity; said contacting collar and said die means cooperating to definetherebetween a molten metal overflow chamber communicating with said diecavity through a narrow, restricted'passage; said platen being movableto a second position in pressure contact with said' collar to insert thecore in the die cavity for applying article-forming molding pressure onmolten metal therein whereby excess metal flows` from said cavity intosaid overow chamber; at least one compensating passage communicatingwith said die cavity and formed in a side of said die means, means forforcing molten metal into said die cavity through said passage formed insaid die means to compensate for metal volume loss dueto cooling causedshrinkage; and ejectormeans forgu'nsea'ting a formed article in saidcavity.

2 Apparatus for high pressure permanent molding of' articles from moltenmetal comprising: split die means defining a core-receiving die cavity;a movable die core carrying platen; means normally biasing a separatecollar movably carried by said platen from contact therewith,

said biased collar being adapted to lock said die vmeansV and remain inlocking contact therewith when said core is being inserted or retractedfrom said cavity, said collar and said die means when in contactcooperating to deline therebetween a molten metal oven-liow chambercommunicating with said die cavity through aV narrow restricted passage,said platen being movable to a second position in pressure contact withsaid collar to insert the core in the die cavity for applyingarticle-forming molding pressure on molten metal therein whereby excessmetal ows from said cavity into said ove'row chamber; at least onecompensating passage communicating with said die cavity and formed in aside of said die means, means for forcing molten metal through saidpassage in said die means into said die cavity to thereby compensate formetal volume loss due to cooling caused shrinkage; and ejector means forparting said split die means and for unseating a formed article in saidcavity.

3. Apparatus for high pressure permanent molding of articles from moltenmetal comprising: a stationary base member; split die means on said basemember defining a core-receiving die cavity therebetween; a'movable diecore-carrying platen disposed to position a die core in said cavity; aseparate collar movably carried by said platen normally biased fromcontact` with said platen, said biased collar being adapted to Contactwith split die means when said platen is in a first position before saidcore is fully inserted or retracted from said die cavity for applyingmolding pressure therein, said collar and said split die meanscooperating to define a metal 8 overiiow chamber communicating-with saiddie cavity through a narrow, restricted passage therebetween; 'saidplaten being adapted to move to asecond position against the force ofthecollar biasing means to thereby contact said collar and position saidcore in said die cavity for applying article-forming molding pressure onmolten metal therein whereby excess metal flows into said overr flowchamber through said restricted passage; at least one:

compensating passage communicating with said die cavity and formed in aside of said die means, piston actuatedl plunger means for forcingmolten metal from said pas 7 sage in saiddie means into said die cavityto thereby' compensate for metal volume loss due to shrinkage; anl

ejector assembly for separating said split die means and for unseating aformed article in said die cavity, and.

said ejector assembly forming the base of said die cavity.`

4. Apparatus for high pressure permanent molding of articles from moltenmetal comprising: a stationary base member; split die means carried bysaid base member defining a core-receiving die cavity therebetween; amov-v able die core-carrying platen disposed to position a die core insaid cavity; a separate collar movably carried by said platen normallybiased from contact with said platen, said biased collar being adaptedto contact and lock said split die means defining said die cavity whensaid platen Ais moved to a rst position before said core is fullyinserted in or retracted from said die cavity for applyingarticle-molding pressure on molten metal therein, said collar and saidsplit die means cooperating to define a metal overliow'chambercommunicating with', said die cavity through a narrow, restrictedpassage'therebetween, said platen being adapted to move to a secondposition against the collar biasing means to thereby contact said collarand position said core kin said die cavity forapplying article-formingmolding pressure on molten metal therein whereby excess metal flows intosaid overflow chamber through said'restricted passage; a pair ofcompensating passages formed in the side of said die means andicommunicating with said die cavity, each of said passages'being adaptedto receive a piston actuated plunger for forcing molten metal from thepassage into said die cavity to thereby compensate for metal volume lossdue to shrinkage; and a die cavity base-defining ejector assembly forunseating a formed article in the die cavity.

5. Ap''pai-"attrsV for aV high pressure permanent molding of articlesfrom molten metal comprising: spit die means defining a core-receivingdie cavity; a reciprocal platen carrying a die core; spring meansnormally biasing a separate collar movably carried by said platen fromcontact therewith, said collar being adapted to lock said die means andremain in locking contact therewith when said core is being inserted orretracted from said cavity for applying molding pressure on molten metalin said cavity, said contacting collar and said die means cooperating'todeline therebetween a molten metal overflow chamber communicating withsaid die cavity through a narrow, restricted passage, said platen beingmovable to a second position in pressure contact with said collar toposition the core in the die cavity for applying articleforming moldingpressure on molten metal therein wherebyexcess metal is displaced fromsaid die cavity into said overflow chamber; a pair of compensatingpassages formed in the sides of said spit die means and in communicationwith said die cavity for receiving metal displaced when said core isinserted in the die cavity, and means for forcing displaced metal fromsaid passages into said die cavity to compensate for cooling causedshrinkage; ejector means for opening said split die means and forunseating a formed article in said cavity including a housing deiiningdie cavity base and a pair ot' pivotable members supporting said housingoperatively responsive to movement of said housing to separate saidsplit die means; and means for moving said ejector assembly to pivotsaid ejector assembly arms and to separate said split die means whensaid core is retracted from said cavity; means fer cooling said cavity.

6. Apparatus for high pressure permanent molding of piston assembliesfrom molten metal comprising: die means defining a core-receiving diecavity; reciprocable die core carrying means; a separate collar movablycarried by said core carrying means normally biased from contacttherewith, said biased collar being adapted t contact said die means andremain in contact therewith when said core is being inserted orretracted from said cavity and to cooperate with said die means todeiine therebetween a molten metal overow chamber communicating withsaid die cavity through a narrow, restricted passage; said core carryingmeans being reciprocably movable to a second position in pressurecontact with` said collar to insert the core in the die cavity forapplying piston-forming pressure to molten metal therein whereby excessmetal flows from said cavity into said overflow chamber; at least onecompensating passage communicating with said die cavity and formed in aside of said die means at the Wrist pin aXis of said piston assembly,and means for forcing molten metal, displaced from said die cavity bysaid core into said compensation from said compensating passage intosaid cavity to compensate for metal volume loss due to cooling-causedshrinkage; and ejector means for unseating a formed piston in saidcavity.

7. Apparatus for high pressure permanent molding of articles from moltenmetal comprising: split die means dening a die cavity and having a pairof compensating passages formed in the sides thereof for receiving metaldisplaced from said die cavity by a core inserted in the die cavity forapplying article-forming pressure to molten metal therein, and meansincluding a movable member in each passage adapted to force saiddisplaced molten metal from said passage into said die cavity tocompensate for metal volume loss due to cooling-caused shrinkage in thedie cavity.

8. Apparatus for high pressure permanent molding of articles from moltenmetal comprising: a die cavity defined by a pair of split die members,said die cavity being adapted to receive a core, a compensating passageformed in the side of each of said split die members for receiving metaldisplaced from said die cavity by said core when inserted into saidcavity for applying article- `forming pressure on molten metal therein,and means including a movable member in each of said passages forforcing said displaced molten metal fromI the passage into the diecavity to compensate for metal volume loss due to cooling-causedshrinkage.

9. Apparatus adapted for high pressure permanent molding of articlescomprising: die means defining a pressurizable die cavity for receivinga core adapted to apply article-forming pressure on molten metal in saiddie cavity, at least one passage formed in a side wall of the die meansand directly communicating with the die cavity for receiving moltenmetal from said die cavity displaced by said core, and a movable memberdisposed in said passage for forcing said displaced molten metal intothe die cavity to compensate for metal volume lost due t0 cooling-causedshrinkage in the die cavity.

l0. Apparatus adapted for high pressure permanent molding comprising:split die means defining a pressurizable die cavity, at lesat onepassage formed in a side wall of the die means and in directcommunication with the die cavity for receiving molten metal displacedby a core inserted in the cavity for applying articleforming pressure onmolten metal therein, and a movable member disposed in the passage forforcing said displaced molten metal from the passage into the die cavityto compensate for metal volume loss due to cooling-caused shrinkage.

l1. Apparatus for high pressure permanent molding of articlescomprising: split die means defining a pressurizable die cavity, aplurality of passages formed in a side of each split die means and indirect communication with the die cavity for receiving molten metaldisplaced by a core inserted in the pressurizable die cavity forapplying article-forming pressure to molten metal in the die cavity, anda movable member disposed in each passage for forcing displaced moltenmetal from the passage into tne die cavity to compensate for metalvolume loss due to cooling-caused shrinkage.

12. Apparatus for high pressure molding comprising: split die meansdefining a pressurizable die cavity, a pair of diametrically opposedpassages formed in a side of the die means and in direct communicationwith the die cavity for receiving molten metal displaced from the diecavity by a core inserted therein for applying articleforming pressureto molten metal in the cavity, and a movable member disposed in eachpassage for forcing said displaced molten metal into the die cavity tothereby compensate for metal volume loss due to cooling-causedshrinkage.

References Cited in the file of this patent UNITED STATES PATENTS1,961,942 Pack June 5, 1934 1,997,074 Novotny Apr. 9, 1935 2,253,822Sundback Aug. 26, 1941 2,415,395 Ulrich Feb. 4, 1947 2,582,260 KutikJan. 15, 1952 2,804,666 Saives Sept. 3, 1957

